Method for the selectively electroplating a strip-shaped, metal support material

ABSTRACT

A method for the continuous selective electroplating of a metallic substrate material ( 10 ) and more particularly of a substrate material band having prestamped contact elements, comprises the following steps:  
     a) the substrate material ( 10 ) is coated in an electrophoretic coating means ( 14 ) with an electrophoretic coating composition selective with at least one composition strip,  
     b) the at least one composition strip is removed at those parts by means of a laser ( 40 ), which are to be electroplated,  
     c) in an electroplating process a metal layer is applied to the areas ( 42 ) deprived of composition in at least one composition strip using selective electroplating and  
     d) the at least one composition strip is then removed.

[0001] The invention relates to a continuous method for the selectiveelectroplating of a metallic substrate material band, and moreparticularly for the electroplating of a substrate material band havingprestamped contact elements.

[0002] In the case of such a method as disclosed in the German patentpublication 19,934,584 A1 the substrate material is firstly completelycoated with coating composition by being either sprayed with it ordipped therein. Then using a laser those parts are freed of coatingcomposition, on which the contact material is to be applied byelectroplating.

[0003] In the case of the known method, both with spraying with thecoating composition and also by dipping therein, only producing acoating composition layer with an uneven thickness there is thedisadvantage. Such a problem becomes more acute in the case ofthree-dimensional substrate material, since here extremely thickdeposits of the coating composition collect more particularly at thecorners and edges. Furthermore, an unbroken coating composition layer,which is absolutely necessary for the method, can only be produced, ifit is relatively thick. In the case of laser removal of material at theparts to be electroplated this will mean either a time-consumingoperation or it will be necessary to utilize high power lasers. Sincethe coating composition layer must be completely removed in the areas tobe electroplated, it is necessary to so set the laser beam that thecoating composition layer is also removed in areas with maximum coatingcomposition thickness. This in turn means that in areas with a smallcoating composition thickness the substrate material will be damaged bythe laser beam. A further disadvantage of the known method is that evenif only very small areas have to be electroplated, very large quantitiesof coating composition will be required for the complete coating of thesubstrate material with a coating composition layer. The relativelylarge thickness of the coating composition layer necessary for producingan unbroken coating composition layer and more particularly thesubstantial accumulations of coating composition in the case ofthree-dimensional substrate materials represent an added difficultyhere. In this case it is necessary to take into account that the coatingcompositions required for such a method are relatively expensive.

[0004] One object of the present invention is to so further develop theknown method that more rapid transit of the band-like substrate materialalong the electroplating line is possible and with a substantially lowercoating composition requirement.

[0005] This object in the to be attained by the invention using themethod steps as defined in claim 1.

[0006] The method in accordance with the invention leads to theadvantage that as regards the electrophoretic coating even withsubstantially smaller coating composition thicknesses an unbrokencoating composition layer may be obtained, such coating compositionhaving an extremely constant coating thickness. Owing to this duringremoval of the coating composition by laser damage to the substratematerial may be effectively prevented. Moreover, the extremely thincoating composition layer may be removed more rapidly and using a lowerpower, something leading to a higher speed of motion of the substratematerial through the equipment. The deposition of the electrophoreticcoating composition on the substrate material takes place extremelyrapidly, something which again renders possible higher throughput ratesof the substrate material. These advantages are furthermore enhanced inas far as only a selective coating composition layer is applied, as forinstance a coating composition strip or a plurality of coatingcomposition strips. These coating composition strips are exclusivelyapplied in areas wherein a layer is to be electroplated on thesubstrate. In addition to savings as regards expensive coatingcomposition there is accordingly more rapid removal of the coatingcomposition at the end of the treatment.

[0007] The electrophoretic coating step only leads, even in the case ofthree-dimensional substrates to even, thin coating composition layerswith the result that it is possible for a selective electroplatingoperation to be performed here as well. Since that the removal ofcoating composition using the action of a laser is able to be controlledsubstantially freely, in addition to electroplating in strips it is alsopossible for electroplating to be performed at points, i. e. inpunctuate areas.

[0008] The measures defined in the dependent claim are in relation toadvantageous further developments and improvements is of the methodindicated in claim 1.

[0009] The substrate material band preferably runs through a cleaningand/or activating and/or swilling unit in order to achieve optimuminitial conditions.

[0010] It is an advantage for a plurality of coating composition stripsto be applied with the same width or with different widths on the sameside or both sides of the substrate material band. The width of suchstrips is in this case able to be exactly set by the electrophoreticcoating method so that by optimizing the required amount of coatingcomposition may be minimized.

[0011] The thickness of the coating composition may be predetermined inaccordance with the voltage applied, the composition of the coating andthe speed of the substrate material, a cataphoretic or anaphoreticdeposit of the coating composition more particularly taking place. Withsuch an exactly set thickness of the coating composition it is alsopossible, by suitably setting the laser beam, to completely remove suchcoating composition layer at the required positions while neverthelesspreventing damage to the substrate material.

[0012] For the electrophoretic deposition of coating compositionscathodes in a housing of the coating composition applying means arepreferably shielded off from the substrate by a slot-like baffle, itbeing possible to adjust the slot width and the distance between thebaffle and the substrate material to get the right width of coatingcomposition strip. Using baffles with a plurality of slots it ispossible to form correspondingly more coating composition strips.

[0013] After applying the coating composition the substrate material ispreferably swilled and dried, more especially in an oven or usingultraviolet light. Furthermore, the substrate material is advantageouslyswilled following the removal of composition with the laser.

[0014] The areas where composition has been removed with the laser maynow be electroplated using one or more of the following selectiveelectroplating methods: selective dipping in an electroplating bath,masking the areas outside the at least one coating composition stripusing mechanical masks, more particularly belt tools, application of theelectrolyte composition by means of wheel technique, spotter techniqueor brush technique.

[0015] Working examples of the invention are represented in the drawingsand will be explained in detail in the following description.

[0016]FIG. 1 is a diagrammatic representation of the individual stationsof a plant for selective electroplating employed in performing themethod of the invention.

[0017]FIG. 2 is a diagrammatic representation of a coating cell for theapplication of a coating composition strip with a predetermined width.

[0018]FIG. 3 is an end-on view of a substrate material band having threecoating composition layers of the front and rear sides.

[0019]FIG. 4 is a perspective view of the substrate material bandrepresented in FIG. 3.

[0020]FIG. 5 is an end-on view of a stamped substrate material bandbearing two coating composition layers.

[0021]FIG. 6 is a perspective representation of the substrate materialband illustrated in FIG. 4.

[0022]FIG. 7 is an end-on view of a three-dimensional substrate materialband having one coating composition strip on the protruding part.

[0023]FIG. 8 is a perspective representation of the substrate materialband viewed in FIG. 7.

[0024]FIG. 9 is an end-on view of a further three-dimensional substratematerial band having one coating composition strip.

[0025]FIG. 10 is a perspective representation of the substrate materialband depicted in FIG. 9.

[0026]FIG. 11 shows an end-on view of a substrate material band havingone coating composition strip, in which a strip area has had coatingcomposition removed from it by laser treatment, and with a masking meansfor selective electroplating.

[0027]FIG. 12 is perspective representation of the substrate materialband illustrated in FIG. 11.

[0028] The electroplating plant depicted in FIG. 1 for the selectiveelectroplating of a substrate material band is designed in the form of aso-called reel-to-reel plant, the metallic substrate material band 10being paid off from a first reel 11 continuously, passed through theplant and to the rear thereof then being wound up on a second reel 12 asa finished band. In this case band speeds of 20 m/min. and higher arepossible.

[0029] Firstly the substrate material band 10 moves through apreparatory station 13, in which it is cleaned, activated and swilleddown.

[0030] Following this the substrate material band 10 is passed through acoating station 14 for coating with composition, where selectiveelectrophoretic coating takes place. The coating station 14 may compriseone or more coating cells 15, as is diagrammatically represented in FIG.2. Such a coating cell in principle comprises a housing, for example inthe form of a capsule, which is so shielded that uncontrolled deposit ofcoating composition in undesired areas is not possible. For this purposebaffles 17 and 18, which like the rest of the housing parts consist ofTeflon or some other non-conductive plastic, are arranged so that theycover over areas, which are not to be coated, of the substrate materialband 10 as regards a plate-like anode 19. Owing to the slot 20 definedby the two baffles 17 and 18 a coating strip is formed byelectrophoretic coating deposition with a corresponding width on thesubstrate material band 10. The anode 19 in this case consists ofstainless steel but a titanium plated one is also suitable.

[0031] The coating cell 15 illustrated is designed for anaphoreticcoating with an anaphoretic composition. Such a composition layer isresistant to acid media such as a nickel, gold or tin plating bath andmay be removed in an alkaline environment. For anaphoretic coating theanode 19 is connected with the positive pole of an electroplatingvoltage, while for the supply of current to the substrate material band19 a contacting means 21 is arranged upstream from the cell. As analternative cataphoretic coating is possible using a cataphoreticcoating composition is possible. The cataphoretic composition isresistant to alkaline media and may be removed in an acid environment.The polarity is reversed, that is to say a cathode takes the place ofthe anode 19.

[0032] The coating cell 15 is so designed that the coating compositionstrips formed and, respectively, the areas coated with the compositionare not damaged after the coating operation. This protection is forexample ensured by the use of guide rollers, not illustrated, which arearranged upstream from and downstream from the coating cell and soexactly position the substrate material both in the vertical and also inthe horizontal direction that the area coated with the composition strip22 does not come into contact with parts of the housing 16. Theclearance between the substrate material band 10 and the baffles 17 and18 is in this case so selected that on the one hand there is asufficient baffle effect and on the other hand there are no points ofcontact.

[0033] The composition, present in a supply tank, not illustrated, issupplied by way of nozzles to the coating cell. A pump located in thesupply tank is connected by way of a pipe with a coating cell, a chokevalve, also not illustrated, being intermediately placed to regulate orcontrol the rate of coating composition feed. A filter arrangement mayalso be present. The composition pump is so designed that by theutilization of low friction materials on all moving part, electriccharges are prevented, as otherwise a deposition of the composition onmoving parts, which might become electrically charged and come intocontact with the composition, might take place.

[0034] In FIGS. 3 through 10 different types of substrate material bandare illustrated as examples, which are provided with differentlyarranged composition strips.

[0035] In the case of the substrate material band as shown in FIGS. 3and 4 three composition strips 24 through 26 of different width areapplied to the front and rear sides. This may be performed either withtandem arranged coating cells 15 or with coating cells, which possess aplurality of slots 20 and baffles and anodes and, respectively, cathodeson either side of the substrate material band 23.

[0036] The substrate material band 27 represented in FIGS. 5 and 6 is soprestamped that individual electrical contacts are already formed, whichafter finishing may be broken or cut off. Two composition strips 28 and29 are applied.

[0037] The substrate material band 30 illustrated in FIGS. 7 and 8 isalso prestamped for the formation of individual electrical contacts,such contact possessing, on one side of a holding strip 31 (which holdsthem together) semicircular protrusions 32 so that the substratematerial band 30 is three-dimensional in structure. One compositionstrip 33 is applied to the outer side of the protrusions 32.

[0038] The substrate material 34 band represented in FIGS. 9 and 10 isas well three-dimensional in shape, holding strips 35 connecting theindividual contact elements 36 at their ends. These contact elements 36are box-like in the middle area, a composition strip 37 extending overthe middle part of the box-like protrusions. The selective compositionstrip (or a plurality thereof) is applied in the case ofthree-dimensional substrate material bands over the entire spatial depthas shown in FIGS. 7 through 10.

[0039] After the application of one or more composition strips thesubstrate material band 10 in accordance with FIG. 1 is passed through adrying station 38. Drying and accordingly partial polymerization isperformed in an oven of the drying station 38, in which an eventemperature distribution is maintained. Alternatively the compositionstrips may also be dried using ultraviolet light and be partiallypolymerized.

[0040] The next step is for the substrate material band 10 to be movedthrough a laser station 39 for selective removal of coating. By means ofthe beam of a laser 40 those composition areas are cleared from thecomposition strip or strips, which are to be later electroplated. Inthis case both stripwise composition removal is possible as well asremoval of composition from individual areas, this being implemented forexample by causing the laser to oscillate over such areas. It isnaturally also possible for a plurality of composition removaloperations in strips to be performed within a composition strip usingthe laser. The dimensional inaccuracies or tolerances of compositionremoval and accordingly of the following electroplating operation areminor and for instance will amount to around 50 microns. The substrateis not damaged by the laser beam and the removal of composition iscomplete. This is ensured by exactly setting the laser as regardsenergy, wavelength, amplitude and duration of the pulses. FIGS. 11 and12 indicate that a strip-like area 42 has been cleared from thecomposition strip 22 applied to the substrate material band 10 in thelaser station 39.

[0041] The substrate material band 10 is now passed through anelectroplating station 43, in which electroplating of the area 42 clearof composition by the laser takes place. This is implemented by a knownselective electroplating method. As shown in FIG. 12 in this case theareas of the substrate material band 10 clear of the composition strip20 are masked by two continuously circulating belts 44. The speed of thebelts 44 is in this case made equal to the speed of passage of thesubstrate material band 10 through the apparatus so that the belts 44keep in step accordingly. The area left free between the two belts 44 isnow wetted with a cloth, a brush or the like with electroplatingsolution and thus electroplated. Dependent on the desired layerthickness this may be performed in a plurality of stages. If thecomposition strip is in a marginal area of the substrate material band10, then it is possible for the selective electroplating also to beperformed by selective dipping in an electroplating bath. As analternative to this other mechanical masks may be utilized, one furtherpossible known method for selective electroplating being on the basis ofa spotter technique and brush technique.

[0042] As a last step the substrate material band 10 is completelycleared of coating composition in a decoating station 45 by passing itthrough a suitable aqueous solution. Dependent on whether a cataphoreticor anaphoretic deposition process has been employed, the aqueoussolution will be acidic or alkaline.

[0043] It is naturally possible to electroplate various differentmaterials such as gold, palladium, silver and zinc onto the substratematerial band 10, which normally consists of brass, copper or a copperalloy. Various different electroplated layers may be placed on top ofone another, the necessary steps for this being performed one aft theother. The substrate material band 10 may for example already bear anelectroplated layer, which is applied in a conventional manner, as inthe form of a selectively plated layer without a coating compositioncovering it.

[0044] The method in accordance with the invention may—as described—beperformed on substrate material bands which in accordance with FIGS. 5through 10 already have prestamped contacts or other elements or have aplain surface, as for example in accordance with FIGS. 3, 4, 11 and 12.In the latter case stamping operations could be performed following theelectroplating operation, although this will require a larger amount ofcoating composition and electroplated metals.

1. A method for the selective continuous electroplating of a metallicsubstrate material band and more particularly of a substrate materialband having prestamped contact elements, in which a) the substratematerial (10, 23, 27, 30 and 34) is coated in an electrophoretic coatingmeans (14 and 15) with an electrophoretic coating composition selectivewith at least one composition strip (22, 24 through 26, 28, 29, 33 and37), b) the at least one composition strip (22, 24 through 26, 28, 39,33 and 37) is removed at those parts (42) by means of a laser (40),which are to be electroplated, c) in an electroplating process a metallayer is applied to the area (42) deprived of composition in at leastone composition strip (22, 24 through 26, 28, 29, 33 and 37) usingselective electroplating and d) the at least one composition strip (22,24 through 26, 28, 29, 33 and 37) is then removed.
 2. The method as setforth in claim 1, characterized in that the substrate material band (10,23, 27, 30 and 34) runs through a cleaning and/or activating and/orswilling stage prior to coating with the composition.
 3. The method asset forth in claim 1, characterized in that a plurality of compositionstrip (24 through 26, 28 and 29) are applied with the same or withdifferent widths on the same side or on both sides of the substratematerial band (23 and 27).
 4. The method as set forth in claim 1,characterized in that the thickness of the composition coating is set inaccordance with the applied voltage, the nature of the composition andthe speed of the substrate material, cataphoretic or anaphoreticcomposition coating being more particularly performed.
 5. The method asset forth in claim 1, characterized in that electrodes (19) in a housing(16) of the composition coating means (14 and 15) are masked from thesubstrate material (10) by a slot-like baffle (17 and 18), the width ofthe composition strip being set in a manner dependent on the slot width(20) and the distance between the baffle (17 and 18) and the substratematerial (10).
 6. The method as set forth in claim 1, characterized inthat the substrate material (10, 23, 27, 30 and 34) is swilled and, moreparticularly in an oven (28) or using ultraviolet light, dried aftercoating.
 7. The method as set forth in claim 1, characterized in thatthe laser removal of composition leads to the formation of strips and/orindividual electroplated areas (42).
 8. The method as set forth in claim1, characterized in that the substrate material (10, 23, 27, 30 and 34)is swilled following the removal of composition by laser.
 9. The methodas set forth in claim 1, characterized in that the areas (42) cleared ofcomposition by the laser (40) are electroplated by one or more of thefollowing selective electroplating methods: selective dipping in anelectroplating bath, masking of the areas outside the at least onecomposition strip by means of mechanical masks (44), more particularlybelt tools, application of the electrolyte by means of a wheeltechnique, a spotter technique, or a brushing technique.
 10. The methodas set forth in claim 1, characterized in that the at least onecomposition strip (22, 24 through 26, 28, 29, 33 and 37) is afterelectroplating completely removed in an alkaline or acid aqueoussolution.